Enhanced ferroelectric properties in Bi-doped K_0.5Na _0.5NbO₃ thin films prepared by pulsed laser deposition

Lead-free ferroelectric Bi-doped K_0.5Na_0.5NbO ₃ (KNN) and undoped KNN films were prepared by pulsed laser deposition. Bi-doped film exhibited good crystallization and improved ferroelectric properties. The dielectric constant and loss tangent were 1038 and 0.138 at 1 kHz, respectively. The remanent polarization (P_r = 28 μC/cm²) of Bi-doped film was about four times larger than that of the undoped film, which attributed to the decrease of oxygen vacancies concentration. The coercive field (E_c = 24 kV/cm) of Bi-doped films was half of the undoped film. The conduction mechanisms of Bi-doped film determined to be Space-Charge-Limited-Current and Poole-Frenkle emission at low and high electric field, respectively.